1. Field of the Invention
The present invention relates to an automatic accompaniment apparatus for an electronic keyboard musical instrument to detect accompaniment contents associated with an operation of the keyboard and to automatically accompany and relates to a fractional chord determination apparatus used in the same.
2. Discussion of Background
As a kind of electronic keyboard musical instrument including an automatic accompaniment function, an electronic keyboard musical instrument where a keyboard portion is divided into a key region for chord detection and a key region for normal performance is known. With this instrument, accompaniment sounds are automatically generated by performing cord detection corresponding to a key operation of the key region for chord detection (region for performing an accompaniment), on the other hand, ordinary music tones (melody tones) are generated corresponding to the key operation of the key region for normal performance (region for performing a melody playing).
Specifically, the generation of the accompaniment sounds in the electronic keyboard musical instrument is performed as follows. That is, at first, the chord detection is performed with a pattern of depressing a key in the chord detection key region. Then, in the chord detection, the chords (including chord root and chord type) corresponding to the depressed pattern of the keys are detected. Next, the preliminarily stored automatic accompaniment pattern data is retrieved from the storing unit, and deployed by a chord deployment operation. The accompaniment pattern data corresponding to the detected chords is generated for the accompaniment sounds by sending the deployed data to a sound source.
In the electronic keyboard musical instrument, a chord detection method is used that is capable of selecting a mode to determine a chord at the point when a single key is depressed (one finger mode described below), and a mode to be determined from a chord when 3 or more keys are depressed, and the like. Furthermore, of this latter chord detection method, a chord change is performed in a fingered when a chord detection of 3 or more keys are depressed on a low-pitched sound side of the keyboard at the split point; in a full keyboard mode, the chord change is performed when the chord detection of 3 or more keys are depressed on the whole keyboard.
In the case where a fractional chord detection mode switch is provided for setting to the fractional chord detection mode, the lowest-pitched sound of the depressed key is detected as a bass. In the fractional chord such as “C/B”, the numerator chord is a high part of the note (chord part) and the denominator chord is a low part of the note (bass part).
Among the modes where a chord is determined by depressing the key chord of 3 or more keys, there is a mode that changes only the denominator chord (the following describes the denominator chord as a bass root) while the numerator chord is fixed when 2 or fewer keys are depressed. The bass root can be specified freely.
However, in general, with keyboard musical instruments, especially in the piano, the left hand is assumed to play a bass line and a chord, and the right hand is assumed to play a melody, a counter line, and the like, in the aforementioned full keyboard mode. The chord is detected point by point with respect to the movement of the melody, and the accompaniment is changed corresponding to the chord detection. This leads to a problem that does not allow a musical performance intended by a performer.